Effects of Strength and Orientation of Steel Fiber on the Fracture Behavior of Steel Fiber Reinforced Concrete

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Various fiber reinforced concretes have been investigated. Their fibers have usually micro-meter order in diameter. Exceptionally, the diameter of steel fiber in SFRC is 0.1-1.0 mm. Therefore, the mechanical behaviors seems to be similar to those of RC.In this investigation, the effects of strength and orientation of steel fiber in mortar on the modulus of elasticity and facture strength of steel fiber reinforced mortar (SFRM) have been studied. The steel fiber used is "SHINKO-steel fiber", whose nominal dimensions are 0.6 mm in dia, 30 mm in length and more than 100 kgf/mm^2 in tensile strength. Various kinds of fibers having other sizes and strengths were also used. The size of specimen was 40X40X160 mm^3, and after aging for more than 28 days, tests were carried out. Results obtained are as follows : (1)Even 1 wt% addition, SF suppress the propergation of cracks. But the amount of SF contributing to strengthening is more than 5wt%. (2)The modulus of elasticity decreases by addition of SF, but by the mixing of optimum amount of expand cement, the decreasing can be controlled. (3)Greased SF dose not contribute to strengthening. (4)The role of SFs having 10 micr-meter in diameter or having 10mm in lengthare small. (5)The longitudinally oliented SF can contribute to strengthening effectively. (6)The modulus of elasticity decreased after autoclave-treatment at 180 ﾟC.